Segmented matrix light-emitting diodes (LEDs) can be used in camera flash or lighting applications (referred to as “adaptive flash”) to illuminate a scene more homogenously. These segmented matrix LEDs devices avoid overexposure by diming the flash light on objects close by and instead use the flash light for objects that are further away. Creating a segmented matrix LED can be expensive unless wafer level processing is used.
To achieve a good contrast in the scene illumination, the optics essentially image the LED onto the scene. Any color variations of the source luminance could lead to color shading in the scene. For white LEDs, typical color variations originate from locally over-converting the light, (i.e., yellow light by e.g. locally thicker phosphor layers). For segmented LEDs, the risk is even higher. Typically, one segment could be switched on while the neighbor segment is still off. With a monolithic matrix LED, the sapphire or phosphor layer could be thought of as made from one piece or block. Unfortunately, this can lead to light guiding inside each of the blocks, i.e. the sapphire and phosphor blocks. Due to different extraction efficiencies in each of the blocks, e.g., blue light from the sapphire block and yellow from the phosphor block, white segments, (which are approximately the targeted sum of blue and yellow light), may have a yellow rim, (“over” converted light in the phosphor layer).
Scene illumination with adaptive flash or adaptive infra-red (IR) requires that the illumination sources, whether IR or visible light sources, be well separated in order to maximize contrast. Wafer level processing of light emitters is preferred for cost and reliability reasons, but widely separating the light emitters on a wafer would waste space and increase costs. Moreover, space is precious in the end products such as mobile phones. The imaging optics would also be challenged if the separation lines in the emitter were too broad. Wafer level processing that ends with closely packed but optically well separated light emitters in the same package is needed.